The following processes are known as processes for producing L-lysine by fermentation using a microorganism belonging to the genus Corynebacterium:    (1) As for processes which use mutants producing L-lysine, those using an S-(2-aminoethyl)-cysteine (hereinafter abbreviated to as “AEC”) resistant mutant [Amino Acid Fermentation (Aminosan Hakko), 1986, p.273, Japan Scientific Societies Press], an L-homoserine-requiring mutant [Amino Acid Fermentation (Aminosan Hakko), 1986, p.273, Japan Scientific Societies Press], a respiration-inhibitor resistant mutant (Japanese Published Examined Patent Application No. 55114/93), a pyrimidine analog resistant mutant (Japanese Published Unexamined Patent Application No. 88094/84), and a purine analog resistant mutant (Japanese Published Examined Patent Application No. 062199/88) have been known.    (2) As for processes which use recombinant bacteria constructed with gene recombination techniques, there have been disclosed a vector plasmid which is self-replicating in a microorganism belonging to the genus Corynebacterium and has a marker which provides a selectable phenotype in the above microorganism, a process for efficiently introducing the vector plasmid, and a process for efficiently producing various L-amino acids including L-lysine by increasing the intracellular copy number of genes involved in the synthesis of the above amino acids using the above vector plasmids (Japanese Published Examined Patent Application No.11959/93, and Japanese Published Examined Patent Application 55155/95).
As for the control of L-lysine biosynthesis, a concerted feedback inhibition by L-lysine and L-threonine against aspartokinase (hereinafter abbreviated to as “AK”) which catalyzes the biosynthesis of aspartyl phosphate from L-aspartic acid is well known. It is known that a microorganism belonging to the genus Corynebacterium having a gene (hereinafter abbreviated to as “a desensitized AK gene”) encoding a mutant AK which has been freed from such a feedback inhibition (hereinafter abbreviated to as “a desensitized AK”) secretes L-lysine extracellularly (Amino Acid Fermentation (Aminosan Hakko), 1986, p.273, Japan Scientific Societies Press). If information of the nucleotide sequence of a mutation is available, a wild type gene can be converted into a mutant gene by utilizing a technique converting a nucleotide sequence into a desired form in a test tube [e.g. a process using a QuickChange Site-Directed Mutagenesis Kit (Stratagene)] with the above information in combination. Recently, the analysis of the above-mentioned desensitized AK gene at the nucleotide sequence level has been reported [Journal of Bacteriology, 175, 4096 (1993); Molecular Microbiology 5, 1197 (1991); Japanese Published Unexamined Patent Application No. 62866/94].